Warren, You and Jobst recently had this exchange about Definite Majority Choice (DMC) and Range voting. You begin by quoting one of Jobst's "15 reasons to support DMC". Range only has this property in a technical sense, in a way that is connected with its technical failure of May's axiom, i.e. it6. Robustness against "noise" candidates.. cloneproof... doesn't reduce to FPP when there are only two candidates. Suppose that in the period leading up to the election it is known for sure that two candidates will stand, A and B. A is a left-wing candidate that is hated by big money and its mass media. B is a centre-right candidate that they like. Reliable but perhaps not widely published polls give A52%, B48%. The method to be used in the election is Range, and with just these two candidates standing the voters have no reason not to give maximum points to their preferred candidate and minimum to the other resulting in a solid win for A. How to change B from being the majority loser to the "super-majority consensus candidate"? Easy! A third candidate, C is nominated. C is a horror far-right candidate. Maybe some of A's supporters are members of some ethnic/racial/religious minority that the C candidate says he's in favour of persecuting. Anyway, now all the mass media have to do now is to convince some of A's supporters that C has some chance of winning the election, or just that they should give a maximised sincere vote. So without C we have: 52: A99, B0 48: B99, A0 A wins 5148 to B4752. With C added and some of A's supporters conned and/or frightened, this could become: 47: A99, B0, C0 05: A99, B98, C0 46: B99, A0, C0 02: C99, B98, C0 Now B wins: B5242, A5148, C198. (Approval is also vulnerable to this scenario.) Note that in this example the voted and sincere (binary) pairwise preferences are A>B 52-48, A>C 52-2, B>C 98-2. I think DMC is a very very good (possibly the best) single-winner method to propose for public office elections if we insist on Condorcet and Mono-raise. Chris Benham . |
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